The present invention relates to an ultrasonic diagnostic apparatus for use in measuring the speed of blood flow in a human body.
In the conventional ultrasonic Doppler method, ultrasonic pulses are emitted in a human body and a receiver extracts. Doppler signals of a desired number from ultrasonic echo signals returned from monitored portions of different depths in a blood vessel. The portions from which the Doppler signals are extracted are chosen between walls of the blood vessel of the human body. By analyzing the frequency of the Doppler signals from various portions in the blood vessel, a distribution of blood flow speed in the blood vessel is obtained. Because of a number of monitored points having different depths, the conventional ultrasonic diagnostic apparatus requires the same number of gate circuits, integration circuits, and sample holding circuits for extracting necessary Doppler signals. Moreover, the same number of gate signal generators are required. Therefore, large scale systems are required for monitoring at many different depths in a blood vessel of a human body.